Profiling PhysX#

PhysX provides a default profiling callback that can be used to collect profiling data and optionally save it to a file. This PxDefaultProfiler is one of the extensions. A snippet named SnippetProfilerConverter is a utility that will convert the output file to a JSON file format that can be viewed in Google Chrome.

Collecting PhysX Profiling Data#

Add the following lines of code to your initialization in order to set up and stream the profiling data to a file:

// Create an output file stream where profiling data will be stored. Writing to the stream occurs when the
// buffer is full or when flush or release is called.
PxDefaultFileOutputStream* outputStream = new PxDefaultFileOutputStream("c:\\users\\work\\profiling.bin");

// Create the profiling callback to receive all of the profiling data.
// The buffer size indicates the number of bytes to allocate per thread for recording all of the profiler events
// received on that thread. If the buffer becomes full, the profiling data is written to the stream, which will cause
// a slight delay. Use a larger buffer size to prevent this, if memory permits. Profiling data is written to the
// stream when the profiler is released.
// The numberOfBuffers specifies how many buffers to pre-allocate. Ideally, there will be more than the number of
// threads, but if a new buffer is needed, one will be allocated, which will take a small amount of time.
PxU32 numberOfBuffers = 16;
PxU32 bufferSize = 32767;
PxDefaultProfiler* profilerCallback = PxDefaultProfilerCreate(*outputStream, numberOfBuffers, bufferSize);

// Register the profiler with PhysX.
PxSetProfilerCallback(profilerCallback);

Run the simulation, and then add the following to your tear down code:

// Release the profiler callback first which streams out all of the data.
profilerCallback->release();

// Now it is safe to delete the output stream.
delete outputStream;

Viewing the Profiler Data#

The previous section explained how the default profiler callback can be used to write PhysX profiling data into a file. The content of this file is in a raw binary format. To view the data, it must be converted to JSON first. The PhysX snippet called SnippetProfilerConverter provides example code that does this conversion. Once the snippet has been compiled, it can be run using the command line:

SnippetProfilerConverter [input_file] [output_file.json]

In Google Chrome, use the URL chrome://tracing and click on the Load button to select the JSON file, or use the newer version, Perfetto, by using https://ui.perfetto.dev/ and select the Open Trace File from the menu.

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